To tell the truth, there can never be an end to buying accessories for your guitar what with a myriad of gig bags, cases, capos, metronomes, tuners, guitar care kits, slides, picks and stands flooding the market.
To begin with, I suppose, we should check the gig bags and guitar case front so that you can save your precious instrument from abuse. Gig bags are made of nylon or vinyl. Some are heavy duty (especially the nylon ones). Some are not. Gig bags are padded on the inside, and some have exterior and interior coverings. Such bags provide much durability. They usually have an external front pocket that can be zipped close. Cases are both lightweight and heavy duty. Some come with an interior and an exterior case. The instrument fits in snugly into the interior case, while the exterior case resists any impact. These are obviously heavy duty.
Capos should be such that you can change their positions quickly and smoothly. The clamp types are gradually becoming smoother to use with their spring-action mechanisms and grips that are cushioned. These clamp capos can be changed by using one hand. There are some capos in the market that have a roller inside the clamp, and which are said to be resisting the usual wear. These are also smooth to use. Apart from these, there are capos that have been made to fit both flat and curved surfaces without doing any harm to the body of the instrument. They also clamp well. I think that you should choose your capo so that it lets you progress unhindered with your progressions!
Slides form an important part of your accessories. From the porcelain to the metallic ones, they help you create beautiful sounds. Some are also made of porcelain. Some are hand crafted. They usually give you years of use. Most of the slides give you a bright tone, while there are some that enhance the middle harmonics. These help to create warm tones. Then there are the glass Blues Bottle slides and the very clever and original reversible slide. The latter lets you flick it around and sort of toggle between fretting and playing with the slide.
There are picks that go better with particular styles of music, and there are some that are favoured more or less by all. The contour, uniformity in thickness, body width, and tip shape all should be taken into consideration so that you can choose the pick that suits you best.
Metronomes and tuners are also essential as accessories. Wooden case metronomes are much more expensive than the ordinary digital ones. Even sophisticated digital metronomes cost a little more than half the price of a wooden metronome. Many digital metronomes have several extra features incorporated into them like a wide range of speed settings and various rhythms. LEDs display the necessary information. In a few models, the metronome and the tuner have been fused to form a single unit.
Stands can be broadly divided into several categories. Apart from the common shaft stands of a large variety, there are the A-frame stands, the racks, the case stands and the hangers.
Last but not the least, comes the guitar care kit in the list of accessories. Choose one with care. Care products are also available separately, and you may opt for them too. There is also a Swiss knife style tool with string cutter, screwdrivers, wrenches and many more that you may need in order to look after your guitar hardware.